Foetal circulation and adaptation at birth

Question 1

What is the function of the placenta?

Answer 1

Fetal homeostasis 
Gas exchange 
Acid base balance 
Nutrient transport to fetus 
Waste product transport from fetus 
Hormone production 
Transport of IgG 
PGE2

Question 2

What is the function of the lungs during foetal development?

Answer 2

They are filled with fluid and un-expanded

Question 3

What type of blood is transported in umbilical veins?

Answer 3

Oxygenated blood as it carries blood from placenta to the foetus

Question 4

What 3 shunts are necessary to foetal life?

Answer 4

Ducutus venosus
Formen ovale
Ductus arteriosus

Question 5

What is the ductus venosus?

Answer 5

Connects the umbilical vein to the inferior vena cana
Nutrients from the placenta don’t need further processing in the liver. The ductus venosus carries the majority of the placental blood straight into the IVC by bypassing portal circulation

Question 6

What is the foramen ovale?

Answer 6

Opening in the atrial spetum connecting the right atrium to the left atrium. Allows blod to flow from the right to left atrium allowing the best oxygenated blood to enter the LA then onto the LV , ascending aorta and carotids. The membranous flap is on the left atrium side

Question 7

What is the ductus arteriosus?

Answer 7

Connects the pulmonary bifurcation to the descending aorta. Only 7% of RV output goes to the lungs. The rest goes via the ductus arteriosus to join the descending aorta. Patency is maintained by circulating PGE2, oxygen saturation and blood flow

Question 8

What adaptations are made in the few minutes following birth?

Answer 8

Baby inflates lungs and cries
Goes from blue to pink
Cord clamped and cut

Question 9

What circulatory changes are made in the first few minutes after birth?

Answer 9

Pulmonary vascular resistance decreases as the lungs physically expand and start to receive more circulating oxygen
Systemic vascular resistance increases as the cord is clamped and cute and threre is more of a CO to the lungs
Foramen ovale closes

Question 10

What causes the duct to constrict?

Answer 10

Increased PO2, decreased flow and decreased PGE2

Question 11

What does the ductus arteriosum end up as?

Answer 11

A fibrous ligament - ligamentum arteriosum

Question 12

What is patent ductus arteriosus?

Answer 12

Failure of duct closure

Question 13

What are the options for patent ductus arteriosus?

Answer 13

Wait and see
NSAIDs (block PGE2)
Surgery

Question 14

Why might you want the ductus arteriosus to stay patent?

Answer 14

Some congenital heart diseases cause a duct dependent circulation

Question 15

How can the duct be kept open?

Answer 15

IV PGE2 can be used to keep the duct open until an alternative shunt is established or definitive surgery is carried out

Question 16

What are examples of congenital heart conditions that require the ductus arteriosus?

Answer 16

Interrupted aortic arch

Coarctation of the aortic arch

Question 17

When does pulmonary resistance reach that of adults?

Answer 17

2-3 months after birth and therefore some problems may only be seen after about 6 weeks post-birth

Question 18

What babies can develop persistent pulmonary hypertension of the newborn?

Answer 18

More likely in sick babies:
Sepsis
Hypoxic ischaemic insult
Meconium aspiration syndrome 
Cold stress 
Can be related to an underlying anatomical abnormality such as congenital diaphragmatic hernia

Question 19

What is persistant pulmonary hypertension of the newborn?

Answer 19

Pulmonary resistance fails to drop after birth and therefore oxygenated blood is shunted across the patnet foramen ovale causing hypoxia

Question 20

What are the clinical signs of PPHN?

Answer 20

Blue baby

Large difference between pre and post ductal oxygen saturation (80% in hands, 60% in feet)

Question 21

How can PPHN be treated?

Answer 21

Ventilation, oxygenation, high systemic blood pressure, inhaled NO, ECLS